JPS6014817B2 - Immersion lance coating material for molten metal refining - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating material for counterfeiting for molten metal refining,
The aim is to provide a lance covering material that has greater durability than conventional products.

The coating material of the present invention will be explained below using a hot metal desulfurization lance as an example.

Generally, the composition of steel is adjusted by blowing it in a converter, but in recent years the proportion of low-sulfur steel being manufactured has increased. In this case, desulfurization in the converter will shorten the life of the converter, so a method is generally implemented in which hot metal is desulfurized in a tear pig iron car or hot metal ladle before charging the hot metal into the converter. In particular, desulfurization in moat pig iron cars is popular because large amounts of hot metal can be processed. The desulfurization is carried out by blowing a desulfurizing agent such as calcium carbide together with a carrier gas such as nitrogen gas into the molten pig iron through a steel pipe or lance coated with a refractory material. The lance is 1350-14
It is used in an operation in which it is placed in a bag in molten pig iron at a high temperature of about 50:00 pm, and after being desulfurized for a predetermined period of time, it is pulled out from the molten pig iron. The conditions required for such a lance coating material are as follows:
First of all, when coating steel pipes, '1) It has speed plasticity but does not have any drawbacks such as dripping when coated on steel pipes, ■ Adhesiveness to steel/guip Examples include having good quality. Furthermore, during actual use, '31: It has an expansion property that can follow the expansion of steel pipes under high temperatures; '4: It has excellent corrosion resistance.'
5} It has excellent spalling resistance, {6} It has sufficient strength, etc. Conventionally, as a coating material for a lance, it is known that water glass is added as a binder to a mixture of fireproof aggregate and binder, and water is added and kneaded.

This conventional lance coating material has sufficient plasticity and adhesion, and therefore has good coating workability. However, during actual use, cracks occur in the diametrical and longitudinal directions of the lance, and the coating material peels off within 2 to 3 charges.
It becomes unusable and its life ends. Alternatively, even if the coating material does not peel off, it has the disadvantage that extremely large cracks may occur, causing serious damage such as puncturing or breakage of the pipe. This drawback is that when the lance is inserted into the welding gun, minute cracks occur in the sheathing material, and these cracks cause erosion of the welding inscription.
Large cracks can grow due to thermal spalling, vibrations when desulfurizing agent is injected, etc., and the lance is pulled out of the molten iron and cooled because the coating material is excessively sintered by the heat of the molten iron. This is thought to be due to the tensile stress generated during shrinkage concentrating on the cracks and enlarging them. In view of the above-mentioned drawbacks of the conventional lance coating materials, the present inventors have found that they satisfy all of the conditions '1] to [6] above and have a long life, and that they also have a long lifespan and are free from holes in pipes due to the occurrence of large cracks. We conducted extensive research with the aim of creating a covering material for lances that can avoid serious problems such as breakage.

As a result, phenol was added as a binder to the refractory aggregate and binder clay.
It has been found that the above object can be achieved when a resin and a bound phosphate are used in combination. The present invention has been completed based on this new knowledge. That is, the present invention provides a molten metal refining infusion characterized by containing (i) refractory aggregate, (ii) bonding viscosity, (iii) powdered phenolic resin, skin condensed phosphate, and M water. This relates to counterfeit covering materials.

The lance coating material of the present invention has appropriate plasticity and good adhesion to pipes, and is excellent in coating workability.

Moreover, it has excellent properties such as expansion ability that can follow the expansion of a steel pipe under the high temperature of a melt gun, corrosion resistance, spalling resistance, and strength, and is highly durable. Furthermore, there is virtually no occurrence of large cracks and resulting pipe holes, breakage, etc. Although the reason why the above-mentioned excellent effects are achieved in the present invention has not yet been completely elucidated, it is thought to be as follows. That is, when the coating material of the present invention dries after being coated on a pipe, a large number of dispersed and very fine cracks that cannot be visually determined occur. This is thought to be because the uniformly dispersed phenol resin condenses to form a network structure due to the action of the condensed phosphate, causing it to shrink slightly. The above-mentioned fine cracks do not grow rapidly due to contact with hot metal, but begin as relatively fine cracks. Moreover, since the coating material of the present invention does not overbrig due to the high heat of the hot metal, the tensile stress generated during cooling after drawing out the lance is uniformly absorbed by the many dispersed fine cracks. is difficult to expand. From the above, it is presumed that the above-mentioned excellent effects are achieved. In the present invention, the refractory aggregates include high alumina raw materials such as competitive alumina, ionized alumina, bauxite, banded shale, synthetic mulaina, kyanite sand, fire clay, chamottes such as frog's-eye chamotte, waxite, magnesia, One or more types of chromite, silicon carbide, graphite, etc. can be used. These refractory aggregates are preferably used after being divided into appropriate particle sizes. For example, it is preferable that the coarse grains be about 30-40%, the medium grains be about 15-20%, and the coarse grains be about 40-60%. In addition, as binding clay, Kibushi clay,
Clays having plasticity such as kaolin, frog's eye clay, and bentonite can be used.

The ratio of the refractory aggregate to the binding clay can be appropriately determined depending on the type of each, but generally the former is 85 to 9 in weight ratio.
The latter is preferably 5 to 15 compared to 5.

In the present invention, it is essential to use a phenol resin and a condensed phosphate together as a binder.

Phenol resin alone has disadvantages such as cracking after coating, problems with shrinkage, and poor strength, while condensed phosphate alone causes dripping and cracking after coating. There are drawbacks such as oversintering and oversintering. As the above-mentioned phenolic resin, novolak-type powdered resins can be used in a wide range, and generally have a molecular weight of 400 to 80.
It is preferable to have a temperature of about 75 to 10 mm, a melting point of about 75 to 10 mm, and a particle size of about 5 to 10 mm.

It is desirable that these phenol resins be blended with a curing agent such as hexamethylenetetramine in an amount of about 5 to 15% in advance. In addition, liquid phenolic resins that use ethylene glycol, methanol, etc. are difficult to impart plasticity to the resulting coating material, dry very slowly at room temperature, and pose a risk of ignition or explosion due to evaporation of the organic solvent during forced drying. It is not desirable because of the presence of The amount of these phenolic resins used may vary depending on the type of refractory aggregate and binding clay, but generally it is 1 part by weight per 10 parts by weight of the refractory aggregate and binding clay.
It is preferable to set it as 5 parts by weight. If it is less than 1 part by weight, the prevention of dripping is insufficient, and if it exceeds 5 parts by weight, drying shrinkage becomes large and large cracks may occur.

As the condensed phosphate, alkali metal salts, particularly sodium salts, such as pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, hexametaphosphoric acid, etc. can be preferably used.

These can be used alone or in combination of two or more. The amount of condensed phosphate used can vary depending on the type of refractory aggregate and binding clay, but usually the total amount of refractory aggregate and binding clay is 10
It is desirable that the amount is about 1 to 5 parts by weight relative to 0 parts by weight.
If it is less than 1 part by weight, the plasticity of the coating material tends to be poor and coating workability tends to be lowered, and if it exceeds 5 parts by weight, there is a strong tendency for oversintering.

Generally, the ratio of the powdered phenol resin to the condensed phosphate is not particularly limited, but the weight ratio is 3:2 to 2:1.
It is preferable to set it as approximately.

The lance coating material of the present invention is manufactured, for example, as follows.

A predetermined amount of refractory aggregate and Sabai sticky material are mixed, a phenol resin and a condensed phosphate are added as a binder and mixed uniformly, and water is further added and kneaded. The amount of water added may be such that the resulting covering material has a predetermined softness, and is generally preferably about 10 to 15 parts by weight per 10 parts by weight of the total amount of fireproof aggregate and bonded clay. . The obtained coating material is coated on an iron pipe according to a conventional method, and dried at room temperature for 24 to 7 hours and at a temperature of 50 to 200 degrees Celsius for about 24 to 9 hours.

In the drying step, rapid evaporation of moisture from the surface of the coating material may cause cracks, so it is preferable to avoid rapid evaporation of moisture. The lance thus obtained is used by being inserted at an angle of 60 to 90 degrees with respect to the horizontal plane of the hot metal.

The present invention will be explained below with reference to Examples and Comparative Examples. Examples 1 and 2 Fire clay composite grains (2.5 to 1.0 side), medium grains (1.0 to 0.1
5 ribs) and characteristic powder (0.15 or less), silicon carbide (0.1
5 skin or less), Shishi graphite, Kibushi sticky material, Kyanite sand, and phenolic resin powder as a binder (molecular weight unevenness 0
, melting point 95 qo, particle size 5-105 qo, center of particle size distribution 20-40 qo, hexamethylenetetramine 7
% blending) and sodium hexametaphosphate, water is added and kneaded to obtain the lance coating material of the present invention.

The obtained coating material was cast into a mold of 40 x 40 x 160 ribs, thrust molded, and dried at 110:00 for 24 hours.

The molded product was then fired at 1400° C. for 1 hour. Table 1 shows the properties of the dried molded product and fired molded product. Also,
The coating material obtained above was coated on an iron pipe measuring 1 inch and having a length of 50 bars.

The coating workability was good and there was no dripping. After coating, it was dried at room temperature for 24 hours at room temperature and about 100 qo, and when the surface of the coating material was visually observed after drying, there were no visible cracks, but when observed with a stereoscopic microscope, Very fine cracks were observed here and there within the field of view, and it was confirmed that a large number of these cracks were dispersed over the entire surface of the coating material. Comparative Example 1 A conventional lance coating material was obtained in the same manner as in Example 1 except that Water Glass No. 2 was used as the binder.

In the same manner as in Example 1, a dry molded product and a fired product thereof were obtained,
These properties are also listed in Table 1. In addition, a 1-inch 0.50 inch iron pipe was coated with the conventional lance coating material, dried in the same manner as in Example 1, and its surface condition was observed. Comparative Example 2 A comparative lance coating material is obtained in the same manner as in Example 1 except that 5 parts by weight of phenolic resin powder is used without using condensed phosphate.

Table 1 shows the properties of the dried molded product of the coating material obtained in the same manner as in Example 1 and the fired product.

The lance coating material of the above comparison was coated on an iron pipe in the same manner as in Example 1 and dried. A crack with a width of 0.5 to 1 foot had appeared on its surface. Comparative example 3 Sodium hexametaphosphate was added without using phenolic resin powder.
A comparative lance coating material was obtained in the same manner as in Example 1 except that the weight part was used.

Table 1 shows the properties of the dried molded product of the coating material obtained in the same manner as in Example 1 and the fired product.

When the above-mentioned comparative coating material was coated on an iron pipe in the same manner as in Example 1, the chain direction in which the coating material dripped easily was extremely large. After being coated, several cracks with a width of 0.5 to 1 side were observed on the surface of the coating material, which was dried in the same manner as in Example 1. Table 1 As is clear from Table 1, the coating materials of the present invention of Examples 1 and 2 exhibited an apparent porosity of 30% or more after firing at 1400 qo, and did not exhibit an extremely high strength value. Oversintering is avoided.

In contrast, conventional coating materials have low apparent porosity;
Moreover, the strength increased significantly, indicating that oversintering had occurred. Example 3 The lance coating material of the present invention obtained in Example 1 was coated with iron vip (3
50 cm, 1 inch), dry at room temperature, and then force dry.

Using the obtained lance, desulfurization treatment of port iron was carried out under the conditions of the second notation, and the life of the lance (i.e., the lance was broken,
Measure the number of charges that become unusable due to holes, large cracks, curvature, etc.

A test is conducted using the seven lances described above, and the life span is calculated from the average value. The results are shown in Table 2. Comparative Example 4 The same machine as Example 3 was used except that the comparative lance coating material obtained in Comparative Example 1 was used, and the lance life was tested.
Shown in the table.

2 As is clear from Table 2, the lance coating material of the present invention (
Example 3) compared to the conventional one (Comparative Example 4), 1
It is possible to extend the lifespan beyond charging.

Claims (1)

[Claims] 1. A dip for smelting molten metal characterized by containing (i) refractory aggregate, (ii) bound clay, (iii) powdered phenolic resin, (iv) condensed phosphate, and (v) water. lance covering material. 2. The usage ratio of refractory aggregate and binding clay is 8 by weight.
5-95: The immersion lance coating material for molten metal refining according to claim 1, wherein the ratio is 5-15. 3. The immersion lance coating for molten metal refining according to claim 1, wherein the amount of powdered phenolic resin used is 1 to 5 parts by weight based on 100 parts by weight of the refractory aggregate and binding clay. Material. 4. The immersion lance for molten metal refining according to claim 1, wherein the amount of condensed phosphate used is 1 to 5 parts by weight based on 100 parts by weight of the refractory aggregate and bonded clay. Covering material. 5 The amount of water used is the total amount of fire-resistant aggregate and bonded clay 10
The immersion lance coating material for molten metal refining according to claim 1, wherein the coating material is 10 to 15 parts by weight relative to 0 parts by weight.